ERW vs Seamless Steel Pipe: Manufacturing, Strength and Cost
ERW vs seamless pipe explained: how each is made, weld seam, wall thickness consistency, pressure and temperature service, sizes, cost and how to choose.
Saudi Steel Work Editorial Team · · 3 min read
Short answer: ERW pipe is formed from steel strip and welded along its length by electric resistance welding, making it economical with consistent wall thickness and good surface finish. Seamless pipe is pierced from a solid billet with no weld, making it preferred for high pressure, high temperature and critical services. Modern ERW is suitable for many pressure applications.
Carbon steel pipe is either welded or seamless. Choosing between them affects cost, availability and suitability for the service.
How ERW pipe is made
- Hot rolled coil is slit to width
- Strip is roll-formed into a tube
- Edges are heated by electric current and forged together
- The weld bead is trimmed
- The seam is often heat-treated, then the pipe is sized, cut and tested
How seamless pipe is made
- A round billet is heated
- It is pierced to form a hollow shell
- The shell is rolled and elongated over a mandrel
- It is sized, heat-treated as required, cut and tested
Comparison
| Factor | ERW | Seamless |
|---|---|---|
| Weld seam | Yes | No |
| Wall thickness uniformity | Very consistent | More variation |
| Surface finish | Smooth | Rougher |
| Typical sizes | Small to medium-large | Small to medium |
| Heavy wall | Limited | Available |
| High temp / pressure | Depends on code | Preferred |
| Cost | Lower | Higher |
| Lead time | Often shorter | Often longer |
Where each is used
ERW: water lines, fire fighting, structural, scaffolding, line pipe (API 5L ERW), hollow sections. Seamless: refinery process piping (ASTM A106), boiler tubes, hydraulic lines, high-pressure gas, sour service where specified.
Large diameter welded pipe
Beyond ERW sizes, pipes are made by LSAW (longitudinal submerged arc welding) or SSAW (spiral) — common for water transmission and pipelines.
Testing
Both should be hydrostatically tested, and ERW seams are typically inspected by ultrasonic or eddy current methods. See NDT for steel.
Choosing
Follow the piping specification. Where it allows either, ERW is usually more economical. See A53 vs A106 and our steel pipes range.